This invention relates to the field of integrated circuit fabrication. More particularly, this invention relates to reducing capacitive coupling between electrically conductive elements in integrated circuits.
New problems are encountered as the size of integrated circuits continues to shrink. For example, materials and processes that were adequate at relatively larger design sizes tend to gradually become less adequate as the size of the integrated circuits gradually decreases. As the size of the integrated circuit is finally reduced to a certain point, some of the previously used materials and processes are found to be inadequate to support proper and reliable operation of the integrated circuit at its new, smaller size.
For example, electrically conductive elements that are spaced apart with an intervening dielectric material tend to form a capacitor. However, when the electrically conductive elements are spaced at a sufficient distance, and the dielectric constant of the intervening dielectric material is sufficiently low, the capacitive coupling between the electrically conductive elements tends to be relatively low and does not tend to effect the operation of the integrated circuit in which the electrically conductive elements are employed. In the past, materials such as silicon oxide provided adequate electrical insulation between electrically conductive elements, without introducing a detrimental amount of capacitive coupling.
However, as the size of the integrated circuit decreases, the electrically conductive elements tend to be placed increasing closer together. Thus, when the same dielectric material as previously employed is used as an electrical insulator between the electrically conductive elements, the capacitive coupling between the electrically conductive elements also tends to increase. Further, the newer, smaller integrated circuits also tend to operate at higher speeds than the older, larger integrated circuits. Therefore, the capacitive coupling between electrically conductive elements tends to have a greater speed impact on the electrical signals being carried on the electrically conductive elements, thus producing a two fold negative impact on the proper and reliable operation of the integrated circuit.
Unfortunately, materials that have been traditionally used to reduce the capacitive coupling between electrically conductive elements also tend to be relatively soft, and tend to not provide adequate structural support for the overlying layers of the integrated circuit that are subsequently formed.
What is needed, therefore, are integrated circuits having reduced capacitive coupling between electrically conductive elements while exhibiting adequate structural support for the subsequently formed overlying layers.
The above and other needs are met by an integrated circuit having an electrically insulating layer of an electrically nonconductive material, where the electrically insulating layer is disposed between at least two electrically conductive elements. The electrically nonconductive material is selected from a group of materials having a k value that decreases when subjected to thermal treatment. The electrically nonconductive material is most preferably a boro siloxane.
In this manner, the decreased k value of the electrically nonconductive material allows the electrically conductive elements to be placed closer to each other than is typically permissible when using dielectric materials having higher k values, such as silicon oxides. Further, the electrically nonconductive material specifically recited above tends to have higher mechanical stability, or in other words tends to be harder, than other so-called low k materials. Thus, the benefits of using a low k dielectric are realized without the detriment of having a layer that is softer and therefore less mechanically sound.
In another aspect, the invention relates to a method of forming an integrated circuit. An electrically insulating layer of an electrically nonconductive material is formed between at least two electrically conductive elements. The electrically nonconductive material is selected from a group of materials having a k value that decreases when subjected to thermal treatment. The electrically nonconductive material is thermally treated to reduce the k value.